ApproachFrom the Tarfala hut up to the Kebnepakte pass (1h), a little bit below the pass on the W side one should start walking up the snow and scree slopes aiming at the point where the ridge gets more defined and narrow (1/2-1h).
Route DescriptionFrom the aforementioned scree slope onto the ridge via a shallow groove (II, simul-climbing, ab 70 m). The ridge consists of several steep butresses, interspersed with the flat "walking" parts. 1st butress is climbed via a chimney on the right (III-IV, ab. 15 m,). This chimney is on the sunny side and thus contains very little snow allthough it can be icy inside. All the following butresses are plastered with the thick layer of snow needles, which makes it necessary to dig for holds and protection. Usually this snow does not hold an icetool or crampon placement. There are 2 butresses of ab. 15-20 m each and then the last one, at about 1900 m, which is the whole ropelength, but is best climbed in two pitches, first a little bit to the left, and then onto the ridge again. The difficulty of "dry" climbing on the butresses would be III-IV, but the snow and rather limited pro (wintertime) make it subjectively somewhat more frightening. After the last butress you're directly below the N summit. From here it's most logical not to climb directly to the N summit, but to slant left (II, simulclimbing, snowy) onto the ridge betweebn Kaskasapakte's main and N summits. The ridge is ab. 200 m, easy but exposed, with some climbing moves. On the whole route there are belay slings on big blocks which serve as indication of one being on the right track.
Descent: either via the W face (steep and sometimes avalanche-prone snow, can be simulclimbed - haven't done this route myself) or (preferrably, since you get closer to the start), via SE face: 15 m abseil from the summit onto the E ridge, then down through the SE face (snow, simulclimbed) along the SE ridge, so that you finally are on top of the rocky triangle described in the SE ridge route, from where one can descent further via the snowy gully on the triangle's E side. S Kaskasapakte's glacier is thus reached and one can then either traverse right (W) to the Kebnepakte's pass (if bivying there) or descent further towards Tarfala hut. I'd recommend starting and finishing at Tarfala - it's only 1 hr longer approach, but you skip carrying the bivy stuff with you.
The best time to climb (already rather warm but less avalanche danger) is the first half of April.